In part, that depends on a dentist's philosophy. But it's the assessment of the patient's mouth and their risk for future cavities, gum disease or oral cancer that ultimately decide the interval between visits, says Dr. Euan Swan, manager of dental programs at the Canadian Dental Association in Ottawa.
"Those that have active disease or are at the highest risk of developing disease should be seen more frequently than those who do not have disease or are at very low risk," explains Swan.
That could mean coming back in six or 12 months for a checkup, although cleanings can be scheduled more often: some dental offices want to see adults to polish their pearlies every four months.
Cleaning is not just for esthetics, but to remove built-up gunk between teeth and below the gum line.
"If dental plaque, which is a biofilm that adheres to the tooth, accumulates over time, it can harden and become calculus or tartar," says Swan. "If that builds up on the tooth surface and the root surface, it can cause irritation to the gums and contribute to periodontal disease."
At the six-month mark, that accumulation is relatively easy to clean off. But going 12 to 18 months between cleanings can make removal more arduous — and that can mean more time in the dental chair.
"But it does depend on the risk of the individual," he says. For instance, adults with gum disease who have been treated by a specialist like a periodontist typically are seen three or four times a year for a deep cleaning aimed at keeping the disease in check.
When it comes to kids, the CDA advises that a child's first dental visit should be scheduled at one year of age or within six months of their first tooth erupting.
"In most cases, a dental exam every six months will let your child's dentist catch small problems early," the CDA says on its website.
Some dentists, Swan says, prefer to see a child when he or she has all their primary — or baby — teeth, which typically happens by age three.
"But the concern is if a child is at high risk of developing tooth decay, if somebody doesn't look at their teeth in the first three years, by (then) they may have tooth decay such that they need to be taken to an operating room and have a general anesthetic to be treated."
A 2013 study by the Canadian Institute for Health Information showed that about 19,000 children aged one to five require surgical treatment each year because of severe tooth decay. In fact, one-third of all day surgeries for preschoolers — who still have their baby teeth — are to perform substantial dental work.
"The feeling is if they can get to the dentist early on ... even if they just have one or two teeth erupted, it's also an opportunity to talk to the parents or the caregiver and give them some guidance regarding nutrition and cleaning techniques," he says.
That advice includes limiting sugar intake, the major cause of cavities.
Once kids start losing baby teeth and their six-year molars are coming in — a period known as mixed dentition — Swan says they should probably have a checkup once a year. And when spaces begin showing between the teeth, it's time to start daily flossing.
How often patients should have dental X-rays is another issue.
For young children, if one or more teeth are not erupting or there's a mass in the mouth, X-rays can show whether teeth are developing properly, says Dr. Ernest Lam, head of oral and maxillofacial radiology at the University of Toronto.
"Really the next time you need anything much more comprehensive is in their teen years, if you have to make an assessment about whether they're developing wisdom teeth," he says. "But in between, it's based on clinical findings during the checkup.
"So if a child is completely asymptomatic and there's no lumps or bumps and there's no complaint of pain, then there's really no reason to."
Lam says there are no strict guidelines about how often an adult should have a panoramic X-ray or a full set of bitewing X-rays, the most common types of dental imaging.
"If you live in a fluoridated community and have no fillings or cavities, the interval time for bitewing X-rays is every two to three years."
But for patients with lots of fillings, a high risk for cavities and complaints of pain, the interval between X-rays can be much less, "maybe six months to a year," says Lam, noting that spot imaging can help reveal what's happening with a tooth, its anchoring jawbone and surrounding connective tissues.
Radiation needs to be used responsibly because there can be a risk to health, he says. "The risk is very low, but it's not zero."
A 2008 study published in the Journal of American Dental Association that calculated the risk of developing a cancer from dental X-rays estimated there is one fatal malignancy per one million panoramic X-rays taken and a similar rate for a full-mouth series of bitewings, which typically involves 19 to 21 X-rays.
Other studies have looked for a potential link between dental imaging and thyroid cancer and meningioma (cancer of the lining of the brain), but showing cause and effect is devilishly difficult, as X-rays aren't the only source of radiation exposure.
Swan says patients should ask their dentist how often they need to be seen for checkups and cleanings — and why — and the same advice goes for X-rays, adds Lam.
"If you don't understand why you are receiving X-rays, whether it's at your physician's request or your dentist's request, you need to ask why," he says. "Because at the end of the day, X-rays are a clinical test and that test should somehow impact positively on how you are treated.
"So if the test has zero impact on what the dentist is going to do to you, then why are you doing it?"
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